Many luminous display devices utilize glowing gas discharges through inert gases such as neon or argon, together with fluorescent phosphor coatings and mercury vapor to provide a wide variety of colors. Traditionally, such devices have made use of thin walled gas tubes to contain the gas discharge, said glass tubes being bent to form the desired character shapes, and terminated with electrodes which are themselves contained within thin walled glass tubes such that the glow discharge tubes are hermetically sealed to the tubes containing the electrodes.
More recently, the use of channels cut into a glass plate, said plate then being sealed to form enclosed channels for the gas discharge have come into use, as taught in U.S. Pat. No. 4,584,501, which also shows the use of electrodes attached externally to the glass plates which contain the gas discharge channel. More recently still, Garjian in U.S. Pat. No. 4,703,574 teaches the use of a center feedthrough plate having termination bores to provide crossover paths to connect plate cavities in front and back plates to form a luminous sign. Garjian, however, also teaches the use of electrode cavities which extend beyond the confines of the plates to contain the electrodes though which electrical power is supplied to the luminous device.
More recently still, O'Mahoney in U.S. Pat. No. 4,839,555 teaches the use of adhesives to seal glass plates together to form a laminated lighting device. O'Mahoney too utilizes separate electrode chambers that are distinct from the body of the laminated display device to contain the electrodes that are necessary to provide the electrical gas discharge which provides the lighting of the device.
None of these disclosures, however, teach the use of electrodes that are internal to and integral with the body of the flat plate neon illumination device. Additionally, none of these disclosures reveal the specific conditions of electrode infrared emissivity and protective thermal resistance which allow the electrodes to be contained integrally within the body of the illumination device.